Whimbrel

Numenius phaeopus (Linnaeus, 1758)

Geographical variation: Two races recognised as occurring in New Zealand: Asiatic whimbrel N.p. variegatus and American whimbrel N.p. hudsonicus. American whimbrel is probably best treated as a separate species from phaeopus (Sangster et al. 2011).

Whimbrels are large shorebirds which migrate to New Zealand from Arctic breeding grounds in small numbers. Most records are during the summer but a few birds occasionally overwinter. In New Zealand they typically associate with bar-tailed godwits, from which they differ in being darker, having a striped head and a strongly down-curved bill.

Identification

Whimbrels are somewhat larger than bar-tailed godwits and recognisable by their down-curved bill and pale stripe down the centre of crown. They are mottled dark brown above, pale below, with much brown streaking on the throat and breast. The head is conspicuously striped, with a pale eyebrow stripe separating the dark eye-stripe and side-crown, and another pale stripe down the centre of the crown. The rump and back pattern is very variable, ranging from largely white with some brown mottling, to heavily streaked brown appearing almost all dark at a distance. Most (possibly all) New Zealand birds are of the Asiatic form, and typically have a pale blaze up the back visible in flight. However, separation of Asiatic and American forms on rump pattern is unreliable as some Siberian birds have completely dark rumps, and it is uncertain whether any American whimbrels occur, or have ever occurred, in New Zealand. The underwing pattern of any ‘dark-rumped’ whimbrel should be checked; both forms have underwngs heavily barred with brown, but American birds have a cinnamon-buff toned underwing (similar to bristle-thighed curlew) while Asiatic birds have a more greyish tone.

Voice: a distinctive seven note whistle: ti-ti-ti-ti-ti-ti-ti.

Similar species: eastern curlew is larger with proportionately much longer bill and no crown stripe. Little whimbrel has crown stripe but bill is finer and only slightly down curved. Bristle-thighed curlew is similar in size and structure but has overall cinnamon-buff colouration, a plain (unbarred) orange-buff rump, and a very different call.

Distribution and habitat

Whimbrels may occur on estuaries throughout New Zealand, but most records are from the northern half of the North Island and Farewell Spit.

Population

About 70 whimbrels occur in New Zealand annually. The East Asian-Australasian Flyway population is estimated at 55,000. Numbers are thought to be declining. Whimbrels have been recorded as vagrant at the Kermadec and Chatham Islands.

Threats and conservation

About 50% of the East Asian-Australasian Flyway whimbrel population stages in the Yellow Sea on northward migration – an area under severe threat from reclamation and pollution.

Breeding

Whimbrels breed on Arctic tundra across Eurasia and North America. A clutch of 4 eggs is laid in a shallow scrape lined with small bits of vegetation.

Behaviour and ecology

In New Zealand, whimbrels occur singly or in small flocks on estuaries, often associating with bar-tailed godwits.

Food

In the non-breeding season whimbrels feed on a wide range of estuarine invertebrates including worms but particularly crabs. They also take small fish.

Identification

A large wader with a medium-sized dark decurved bill, a pale stripe on the centre of the crown, and a pale eyebrow stripe separating the dark eye-stripe and side-crown. The upperparts are mottled dark brown contrasting pale underparts with brown streaking on the throat and breast, and the rump and back pattern is highly variable.